Device, system and method of multi-user multi-input-multi-output wireless communication

ABSTRACT

Device, system, and method of multi-user multi-input-multi-output (MIMO) wireless communication. In some embodiments, a wireless communication device ( 102 ) may be capable of receiving a plurality of channel feedback transmissions from a plurality of user devices ( 104, 106, 108 ) respectively, wherein a channel feedback transmission from a user device of the user devices includes partial information relating to a MIMO channel matrix between the wireless communication unit and the user device; and transmitting a multi -user MIMO transmission to the plurality of user devices according to a MIMO beamforming scheme, wherein the MIMO beamforming scheme is based on the plurality of channel feedback transmissions.

BACKGROUND

A wireless communication system may implement a Multi-User (MU)Multi-Input-Multi-Output (MIMO) scheme.

The multi-user MIMO scheme is considered as an effective way to achievehigh throughput performance in wireless communication systems.

A wireless communication device (“station”) may utilize a plurality oftransmit antennas to simultaneously transmit MIMO transmissions to aplurality of wireless communication devices (“users”), each utilizing aplurality of receive antennas; and/or a plurality of receive antennas tosimultaneously receive MIMO transmissions from the plurality of users.

An adaptive beamforming algorithm, e.g., a Block Diagonalization (BD)beamforming algorithm or a Regularized Block Diagonalization (RBD)beamforming algorithm, may be utilized at the station to support morethan one spatial stream per user of the multi-user MIMO transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

For simplicity and clarity of illustration, elements shown in thefigures have not necessarily been drawn to scale. For example, thedimensions of some of the elements may be exaggerated relative to otherelements for clarity of presentation. Furthermore, reference numeralsmay be repeated among the figures to indicate corresponding or analogouselements. The figures are listed below.

FIG. 1 is a schematic block diagram illustration of a system inaccordance with some demonstrative embodiments.

FIG. 2 is a schematic flow-chart illustration of a method of wirelesscommunication, in accordance with some demonstrative embodiments.

FIG. 3 is a schematic illustration of a graph depicting ergodic capacityas a function of signal-to-noise-ratio (SNR) for a multi-usermulti-input-multi-output (MIMO) transmission utilizing channel feedbacksincluding partial MIMO channel information, in accordance with somedemonstrative embodiments.

FIG. 4 is a schematic flow-chart illustration of a method of wirelesscommunication, in accordance with some demonstrative embodiments.

FIG. 5 is a schematic illustration of a graph depicting ergodic capacityas a function of SNR for a multi-user MIMO transmission utilizingchannel feedbacks including channel quality indications and partial MIMOchannel information, in accordance with some demonstrative embodiments.

FIG. 6 is a schematic illustration of an article of manufacture, inaccordance with some demonstrative embodiments.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of some embodiments.However, it will be understood by persons of ordinary skill in the artthat some embodiments may be practiced without these specific details.In other instances, well-known methods, procedures, components, unitsand/or circuits have not been described in detail so as not to obscurethe discussion.

Discussions herein utilizing terms such as, for example, “processing”,“computing”, “calculating”, “determining”, “establishing”, “analyzing”,“checking”, or the like, may refer to operation(s) and/or process(es) ofa computer, a computing platform, a computing system, or otherelectronic computing device, that manipulate and/or transform datarepresented as physical (e.g., electronic) quantities within thecomputer's registers and/or memories into other data similarlyrepresented as physical quantities within the computer's registersand/or memories or other information storage medium that may storeinstructions to perform operations and/or processes.

The terms “plurality” and “a plurality” as used herein include, forexample, “multiple” or “two or more”. For example, “a plurality ofitems” includes two or more items.

Some embodiments may be used in conjunction with various devices andsystems, for example, a video device, an audio device, an audio-video(A/V) device, a Set-Top-Box (STB), a Blu-ray disc (BD) player, a BDrecorder, a Digital Video Disc (DVD) player, a High Definition (HD) DVDplayer, a DVD recorder, a HD DVD recorder, a Personal Video Recorder(PVR), a broadcast HD receiver, a video source, an audio source, a videosink, an audio sink, a stereo tuner, a broadcast radio receiver, adisplay, a flat panel display, a Personal Media Player (PMP), a digitalvideo camera (DVC), a digital audio player, a speaker, an audioreceiver, an audio amplifier, a data source, a data sink, a DigitalStill camera (DSC), a Personal Computer (PC), a desktop computer, amobile computer, a laptop computer, a notebook computer, a tabletcomputer, a server computer, a handheld computer, a handheld device, aPersonal Digital Assistant (PDA) device, a handheld PDA device, anon-board device, an off-board device, a hybrid device, a vehiculardevice, a non-vehicular device, a mobile or portable device, a consumerdevice, a non-mobile or non-portable device, a wireless communicationstation, a wireless communication device, a wireless Access Point (AP),a wired or wireless router, a wired or wireless modem, a wired orwireless network, a wireless area network, a Wireless Video Area Network(WVAN), a Local Area Network (LAN), a Wireless LAN (WLAN), a PersonalArea Network (PAN), a Wireless PAN (WPAN), devices and/or networksoperating in accordance with existing WirelessHD™ and/orWireless-Gigabit-Alliance (WGA) specifications and/or future versionsand/or derivatives thereof, devices and/or networks operating inaccordance with existing IEEE 802.11 (IEEE 802.11-1999. Wireless LANMedium Access Control (MAC) and Physical Layer (PHY) Specifications),IEEE 802.11n, IEEE802.11 task group ac (TGac) (“ IEEE802.11-09/0308r12-TGac Channel Model Addendum Document”), IEEE 802.11 task group ad(TGad), IEEE 802.16 (IEEE-Std 802.16, 2009 Edition, Air Interface forFixed Broadband Wireless Access Systems), IEEE 802.16e (IEEE-Std802.16e, 2005 Edition, Physical and Medium Access Control Layers forCombined Fixed and Mobile Operation in Licensed Bands), IEEE 802.16m(amendment to IEEE Std 802.16-2009, developed by Task Group m) standardsand/or future versions and/or derivatives thereof, devices and/ornetworks operating in accordance with existing 3rd GenerationPartnership Project (3GPP), 3GPP Long term Evolution (LTE), e.g., the3GPP LTE Rel-8, and/or any other suitable protocol or standard, unitsand/or devices which are part of the above networks, one way and/ortwo-way radio communication systems, cellular radio-telephonecommunication systems, Wireless-Display (WiDi) device, a cellulartelephone, a wireless telephone, a Personal Communication Systems (PCS)device, a PDA device which incorporates a wireless communication device,a mobile or portable Global Positioning System (GPS) device, a devicewhich incorporates a GPS receiver or transceiver or chip, a device whichincorporates an RFID element or chip, a MIMO transceiver or device, adevice having one or more internal antennas and/or external antennas,Digital Video Broadcast (DVB) devices or systems, multi-standard radiodevices or systems, a wired or wireless handheld device (e.g.,BlackBerry, Palm Treo), a Wireless Application Protocol (WAP) device, orthe like.

Some embodiments may be used in conjunction with one or more types ofwireless communication signals and/or systems, for example, RadioFrequency (RF), Infra Red (IR), Frequency-Division Multiplexing (FDM),Orthogonal FDM (OFDM), Time-Division Multiplexing (TDM), Time-DivisionMultiple Access (TDMA), Extended TDMA (E-TDMA), General Packet RadioService (GPRS), extended GPRS, Code-Division Multiple Access (CDMA),Wideband CDMA (WCDMA), CDMA 2000, single-carrier CDMA, multi-carrierCDMA, Multi-Carrier Modulation (MDM), Discrete Multi-Tone (DMT),Bluetooth®, Global Positioning System (GPS), Wi-Fi, Wi-Max, ZigBee™,Ultra-Wideband (UWB), Global System for Mobile communication (GSM), 2G,2.5G, 3G, 3.5G, Enhanced Data rates for GSM Evolution (EDGE), 3GPP, 3GPPLTE, or the like. Other embodiments may be used in various otherdevices, systems and/or networks.

The term “wireless device” as used herein includes, for example, adevice capable of wireless communication, a communication device capableof wireless communication, a communication station capable of wirelesscommunication, a portable or non-portable device capable of wirelesscommunication, or the like. In some embodiments, a wireless device maybe or may include a peripheral that is integrated with a computer, or aperipheral that is attached to a computer. In some embodiments, the term“wireless device” may optionally include a wireless service.

Some embodiments may be implemented for wireless transmission ofsuitable content between two or more devices. In one embodiment, thecontent may include media content, for example, audio and/or videocontent, e.g., High Definition Television (HDTV) content, and the like.In other embodiments, the content may include any other suitable data,information and/or signals.

Reference is now made to FIG. 1, which schematically illustrates a blockdiagram of a system 100 in accordance with some demonstrativeembodiments.

As shown in FIG. 1, in some demonstrative embodiments, system 100 mayinclude a wireless communication network including one or more wirelesscommunication devices, e.g., wireless communication devices 102, 104,106 and/or 108, capable of communicating content, data, informationand/or signals over at least one suitable wireless communicationchannel, for example, a radio channel, an IR channel, a RF channel, a

Wireless Fidelity (WiFi) channel, and the like. One or more elements ofsystem 100 may optionally be capable of communicating over any suitablewired communication links.

In some demonstrative embodiments, system 100 may communicate, manageand/or process information in accordance with one or more suitablecommunication protocols. For example, system 100 may implement one ormore of a medium access control (MAC) protocol, a Physical LayerConvergence Protocol (PLCP), a Simple Network Management Protocol(SNMP), an Asynchronous Transfer Mode (ATM) protocol, a Frame Relayprotocol, a Systems Network Architecture (SNA) protocol, a TransportControl Protocol (TCP), an Internet Protocol (IP), a Hypertext TransferProtocol (HTTP), a User Datagram Protocol (UDP), and the like.

In some demonstrative embodiments, wireless communication devices 102,104, 106 and/or 108 may include, for example, a PC, a desktop computer,a mobile computer, a laptop computer, a notebook computer, a tabletcomputer, a server computer, a handheld computer, a handheld device, aPDA device, a handheld PDA device, an on-board device, an off-boarddevice, a hybrid device (e.g., combining cellular phone functionalitieswith PDA device functionalities), a consumer device, a vehicular device,a non-vehicular device, a mobile or portable device, a non-mobile ornon-portable device, a cellular telephone, a PCS device, a PDA devicewhich incorporates a wireless communication device, a mobile or portableGPS device, a DVB device, a relatively small computing device, anon-desktop computer, a “Carry Small Live Large” (CSLL) device, an UltraMobile Device (UMD), an Ultra Mobile PC (UMPC), a Mobile Internet Device(MID), an “Origami” device or computing device, a device that supportsDynamically Composable

Computing (DCC), a context-aware device, a video device, an audiodevice, an A/V device, a STB, a BD player, a BD recorder, a DVD player,a HD DVD player, a DVD recorder, a HD DVD recorder, a PVR, a broadcastHD receiver, a video source, an audio source, a video sink, an audiosink, a stereo tuner, a broadcast radio receiver, a flat panel display,a PMP, a DVC, a digital audio player, a speaker, an audio receiver, agaming device, an audio amplifier, a data source, a data sink, a DSC, amedia player, a Smartphone, a television, a music player, an AP, a basestation, or the like.

In some demonstrative embodiments, wireless communication device 110 mayinclude a wireless communication unit 110 to perform Multi-User (MU)Multi-Input- Multi-Output (MIMO) wireless communication with wirelesscommunication devices 104, 106 and/or 108, and/or with one or more otherwireless communication devices, e.g., as described below. Wirelesscommunication devices 104, 106 and/or 108 may include a wirelesscommunication unit 124 to perform MU MIMO wireless communication withwireless communication device 102 and/or with one or more other wirelesscommunication devices, e.g., as described below.

In some demonstrative embodiments, wireless communication devices 102,104, 106 and/or 108 may also include, for example, one or more of aprocessor 118, an input unit 114, an output unit 116, a memory unit 120and a storage unit 122. Wireless communication devices 102, 104, 106and/or 108 may optionally include other suitable hardware componentsand/or software components. In some demonstrative embodiments, some orall of the components of one or more of wireless communication devices102, 104, 106 and/or 108 may be enclosed in a common housing orpackaging, and may be interconnected or operably associated using one ormore wired or wireless links. In other embodiments, components of one ormore of wireless communication devices 102, 104, 106 and/or 108 may bedistributed among multiple or separate devices.

Processor 118 includes, for example, a Central Processing Unit (CPU), aDigital Signal Processor (DSP), one or more processor cores, asingle-core processor, a dual-core processor, a multiple-core processor,a microprocessor, a host processor, a controller, a plurality ofprocessors or controllers, a chip, a microchip, one or more circuits,circuitry, a logic unit, an Integrated Circuit (IC), anApplication-Specific IC (ASIC), or any other suitable multi-purpose orspecific processor or controller. Processor 114 executes instructions,for example, of an Operating System (OS) of wireless communicationdevices 102, 104, 106 and/or 108 and/or of one or more suitableapplications.

Input unit 114 includes, for example, a keyboard, a keypad, a mouse, atouch-pad, a track-ball, a stylus, a microphone, or other suitablepointing device or input device. Output unit 116 includes, for example,a monitor, a screen, a flat panel display, a Cathode Ray Tube (CRT)display unit, a Liquid Crystal Display (LCD) display unit, a plasmadisplay unit, one or more audio speakers or earphones, or other suitableoutput devices.

Memory unit 120 includes, for example, a Random Access Memory (RAM), aRead Only Memory (ROM), a Dynamic RAM (DRAM), a Synchronous DRAM(SD-RAM), a flash memory, a volatile memory, a non-volatile memory, acache memory, a buffer, a short term memory unit, a long term memoryunit, or other suitable memory units. Storage unit 122 includes, forexample, a hard disk drive, a floppy disk drive, a Compact Disk (CD)drive, a CD-ROM drive, a DVD drive, or other suitable removable ornon-removable storage units. Memory unit 120 and/or storage unit 122,for example, may store data processed by wireless communication devices102, 104, 106 and/or 108.

In some demonstrative embodiments, wireless communication units 110and/or 124 include, for example, one or more wireless transmitters,receivers and/or transceivers able to send and/or receive wirelesscommunication signals, RF signals, frames, blocks, transmission streams,packets, messages, data items, and/or data. For example, wirelesscommunication units 110 and/or 124 may include or may be implemented aspart of a wireless Network Interface Card (NIC), and the like.

In some demonstrative embodiments, wireless communication unit 110 mayinclude, or may be associated with, a plurality of antennas 120.Wireless communication devices 104, 106 and/or 108 may include, or maybe associated with, a plurality of antennas 126, 128 and/or 130,respectively. Antennas 120, 126, 128 and/or 130 may include any type ofantennas suitable for transmitting and/or receiving wirelesscommunication signals, blocks, frames, transmission streams, packets,messages and/or data. For example, antennas 120, 126, 128 and/or 130 mayinclude internal and/or external RF antennas, dipole antennas, monopoleantennas, omni-directional antennas, end fed antennas, circularlypolarized antennas, micro-strip antennas, diversity antennas, anysuitable configuration, structure and/or arrangement of one or moreantenna elements, components, units and/or arrays, e.g., a phased arrayantenna, a single element antenna, a set of switched beam antennas, andthe like. In some embodiments, antennas 120, 126, 128 and/or 130 mayimplement transmit and receive functionalities using separate transmitand receive antenna elements. In some embodiments, 120, 126, 128 and/or130 may implement transmit and receive functionalities using commonand/or integrated transmit/receive elements.

In some demonstrative embodiments, wireless communication unit 110 maybe configured to transmit a MU MIMO transmission 113 to a plurality ofuser devices, e.g., devices 104, 106 and/or 108, according to a MIMObeamforming (BF) scheme.

In some demonstrative embodiments, MU MIMO transmission 113 may includetwo or more transmission streams directed to each of devices 104, 106and/or 108.

In some demonstrative embodiments, wireless communication unit 110 maydetermine the BF scheme to be used for transmitting MU MIMO transmission131 to wireless communication devices 104, 106 and/or 108 e.g., asdescribed below.

In order to enable a transmitter to perform a MU MIMO transmission to aplurality of users according to a beamforming scheme, e.g., theconventional Block Diagonalization (BD) beamforming scheme and/or theconventional Regularized BD (RBD) beamforming scheme, the transmitter isto be provided with the entire channel matrix between the transmitterand each of the users. However, transmitting the entire channel matrixfrom each used back to the transmitter may be cumbersome, may increasean overhead of the MU MIMO communication, may reduce throughput, mayincrease interference and/or may have any other adverse effects on theMU MIMO communication.

In some demonstrative embodiments, a user device of system 100 may beconfigured to transmit to wireless communication unit 110 a channelfeedback transmission including partial information relating to a MIMOchannel matrix between wireless communication unit 110 and the userdevice. For example, wireless communication unit 124 may be configuredto transmit to wireless communication unit 110 a channel feedbacktransmission including partial information relating to a MIMO channelmatrix between wireless communication unit 110 and wirelesscommunication unit 124, e.g., as described below.

In some demonstrative embodiments, wireless communication unit 110 mayreceive a plurality of channel feedback transmissions from the pluralityof user devices, respectively, wherein a channel feedback transmissionfrom a user device of the user devices includes partial informationrelating to a MIMO channel matrix between the wireless communicationunit and the user device. For example, wireless communication unit 110may receive a first channel feedback transmission from used device 104including partial information relating to a first MIMO channel matrixbetween wireless communication unit 110 and user device 104; a secondchannel feedback transmission from used device 106 including partialinformation relating to a second MIMO channel matrix between wirelesscommunication unit 110 and user device 106; and/or a third channelfeedback transmission from used device 108 including partial informationrelating to a third MIMO channel matrix between wireless communicationunit 110 and user device 108, e.g., as described below.

In some demonstrative embodiments, the channel feedback transmissionfrom a user device may represent a plurality of eigenvectorscorresponding to the channel matrix between wireless communication unit110 and the user device. For example, the first channel feedbacktransmission may represent a plurality of eigenvectors corresponding tothe MIMO channel matrix between wireless communication unit 110 and userdevice 104; the second channel feedback transmission may represent aplurality of eigenvectors corresponding to the MIMO channel matrixbetween wireless communication unit 110 and user device 106; and/or thethird channel feedback transmission may represent a plurality ofeigenvectors corresponding to the MIMO channel matrix between wirelesscommunication unit 110 and user device 108.

In some demonstrative embodiments, a number of the plurality ofeigenvectors represented by the channel feedback transmission from theuser device may be equal to a number of transmission streams of MU MIMOtransmission 113, which are directed to the user device. For example,the number of eigenvectors represented by the first channel feedbacktransmission from user device 104 may be equal to the number oftransmission streams of MU MIMO transmission 113, which are directed touser device 104; the number of eigenvectors represented by the secondchannel feedback transmission from user device 106 may be equal to thenumber of transmission streams of MU MIMO transmission 113, which aredirected to user device 106; and/or the number of eigenvectorsrepresented by the third channel feedback transmission from user device108 may be equal to the number of transmission streams of MU MIMOtransmission 113, which are directed to user device 108.

In some demonstrative embodiments, the channel feedback transmissionfrom a user device may represent a plurality of dominant eigenvectorscorresponding to a respective plurality of dominant eigenvalues of thechannel matrix between wireless communication unit 110 and the userdevice. For example, the first channel feedback transmission mayrepresent a plurality of dominant eigenvectors corresponding to arespective plurality of dominant eigenvalues of the MIMO channel matrixbetween wireless communication unit 110 and user device 104; the secondchannel feedback transmission may represent a plurality of dominanteigenvectors corresponding to a respective plurality of dominanteigenvalues of the MIMO channel matrix between wireless communicationunit 110 and user device 106; and/or the third channel feedbacktransmission may represent a plurality of dominant eigenvectorscorresponding to a respective plurality of dominant eigenvalues of theMIMO channel matrix between wireless communication unit 110 and userdevice 108.

In some demonstrative embodiments, the channel feedback transmissionfrom the user device may include or represent quantized values of theplurality of dominant eigenvectors.

In some demonstrative embodiments, the feedback transmission from a userdevice may include a codebook index representing a plurality ofpredefined eigenvectors corresponding to the plurality of eigenvectorsof the MIMO channel matrix between wireless communication unit 110 andthe user device. For example, the first channel feedback transmissionmay include a codebook index, e.g., a single codebook index,representing a predefined set of codebook eigenvectors corresponding tothe plurality of eigenvectors of the MIMO channel matrix betweenwireless communication unit 110 and user device 104; the second channelfeedback transmission may include a codebook index, e.g., a singlecodebook index, representing a predefined set of codebook eigenvectorscorresponding to the plurality of eigenvectors of the MIMO channelmatrix between wireless communication unit 110 and user device 106;and/or the third channel feedback transmission may include a codebookindex, e.g., a single codebook index, representing a predefined set ofcodebook eigenvectors corresponding to the plurality of eigenvectors ofthe MIMO channel matrix between wireless communication unit 110 and userdevice 108.

In some demonstrative embodiments, the codebook index may include asuitable Single User (SU) MIMO codebook index, e.g., in the form of apreferred matrix index, which may be defined for a SU MIMO transmissionscheme. In one example, the codebook index may include a codebook indexin accordance with the IEEE 802.16 standards, e.g., the IEEE 802.16mstandard, the 3GPP LTE, e.g., the 3GPP LTE Rel-8, and/or any othersuitable protocol or standard.

In some demonstrative embodiments, wireless communication unit 110 maybe configured to determine the MIMO beamforming scheme of MU MIMOtransmission 113 based on the plurality of channel feedbacktransmissions received from wireless communication devices 104, 106and/or 108, e.g., as described below.

In some demonstrative embodiments, wireless communication unit 110 maybe configured to determine the MIMO beamforming scheme of MU MIMOtransmission 113 based on a Modified BD (MBD) algorithm and/or aModified RBD (MRBD) algorithm, which may utilize partial informationrelating to the MIMO channel matrix between wireless communication unit110 and the user devices, e.g., as described below.

In some demonstrative embodiments, the channel feedback transmissionfrom a user device may represent an eigenvector matrix of N_(SS)dominant quantized eigenvectors of the MIMO channel matrix betweenwireless communication unit 110 and the user device, wherein N_(SS)denotes the number of transmission streams of transmission 113 directedto the user device. In one example, wireless communication unit 110 mayreceive from wireless communication unit 124 a suitable codebook indexrepresenting the matrix of N_(SS) dominant quantized eigenvectors of theMIMO channel matrix between wireless communication unit 110 and wirelesscommunication device 104.

In some demonstrative embodiments, wireless communication unit 110 maydetermine, e.g., based on the plurality of channel feedbacktransmissions, a plurality of eigenvector matrices, denoted V_(i), eachincluding N_(SS) dominant quantized eigenvectors corresponding to arespective i-th user device, wherein i=1 . . . K, and wherein K denotesthe number of users intended to receive MU MIMO transmission 113. In oneembodiment, wireless communication unit 110 may receive K codebookindices from the K user devices, respectively, and determine K matricesV_(i) based on the K codebook indices, respectively. In otherembodiments, wireless communication unit 110 may determine matricesV_(i) based on any other suitable channel feedback.

In some demonstrative embodiments, wireless communication unit 110 maydetermine the MIMO beamforming scheme based on the plurality ofeigenvectors, e.g., the N_(SS) dominant quantized eigenvectors,corresponding to the i-th user device, and based on a plurality ofinterference matrices corresponding to the plurality of user devices,respectively. An interference matrix corresponding to the i-th userdevice may include a plurality of eigenvectors corresponding to otheruser devices of the plurality of user devices, e.g., as described below.

In some demonstrative embodiments, an interference matrix, denoted{tilde over (V)}_(i), may be defined with respect to the i-th userdevice, e.g., as follows:

{tilde over (V)} _(i) =[V ₁ . . . V _(i−1) , V _(i+1) . . . V _(K)]  (1)

In some demonstrative embodiments, Single Value Decomposition (SVD) ofthe interference matrix {tilde over (V)}_(i) may yield:

{tilde over (V)} _(i) =Ũ _(i){tilde over (Σ)}_(i) {tilde over (W)} _(i)^(H)   (2)

wherein Ũ_(i) denotes a (M_(T)-by-M_(T)) unitary matrix over a field,denoted M, which includes the matrix {tilde over (V)}_(i); wherein M_(T)denotes a number of transmit antennas 112 utilized by wirelesscommunication unit 110 to perform transmission 113; wherein {tilde over(Σ)}_(i) denotes a (M_(T)-by-(K−1)N_(SS)) diagonal matrix withnonnegative real numbers on the diagonal; wherein {tilde over (W)}_(i)denotes a ((K−1)N_(SS)-by-(K−1)N_(SS)) unitary matrix over M; andwherein {tilde over (W)}_(i) ^(H) denotes a conjugate of {tilde over(W)}^(i).

In some demonstrative embodiments, a matrix, denoted Ũ_(i) ⁽¹⁾, may bedetermined as a basis of a space spanned by all the dominanteigenvectors of the users other than the i-th user. For example, thematrix Ũ_(i) ⁽¹⁾ may include a set of eigenvectors of the matrix Ũ_(i)corresponding to non-zero singular values.

In some demonstrative embodiments, a first precoding vector, denotedV_(i1)′, may be determined, for example, by orthogonalizing a firsteigenvector, denoted V_(i1), of the matrix V_(i), e.g., the eigenvectorcorresponding to the maximal eigenvalue of the MIMO channel matrix ofthe i-th user, to the basis Ũ_(i) ⁽¹⁾.

In some demonstrative embodiments, an updated basis, denoted U_(i1)′,may be determined based on the basis Ũ_(i) ⁽¹⁾ and the precoding vectorV_(i1)′. For example, the updated basis U_(i1)′ may be determined byconcatenating the basis Ũ_(i) ⁽¹⁾ with the first precoding vectorV_(i1)′, e.g., as follows:

U _(i1) ′=[Ũ _(i) ⁽¹⁾ V _(i1)′]  (3)

In some demonstrative embodiments, a second precoding vector, denotedV_(i2)′, may be determined, for example, by orthogonalizing a secondeigenvector, denoted V_(i2), of the matrix V_(i), e.g., the eigenvectorcorresponding to the second maximal eigenvalue of the MIMO channelmatrix of the i-th user, to the updated basis U_(i1)′; and a secondupdated basis, denoted U_(i2)′, may be determined by concatenating theupdated basis U_(i1)′ with the second precoding vector V_(i2)′ , e.g.,as follows:

U _(i2) ′=[U _(i1) ′V _(i2)′]  (4)

In some demonstrative embodiments, the operations described above may berepeated, e.g., to determine N_(SS) precoding vectors. For example, anl-th precoding vector, denoted V_(i1)′, wherein 1=2 . . . N_(SS), may bedetermined, for example, by orthogonalizing an l-th eigenvector, denotedV_(i1), of the matrix V_(i), e.g., the eigenvector corresponding to thel-th maximal eigenvalue of the MIMO channel matrix of the i-th user, tothe updated basis U_(i(i−1))′, which may be determined by concatenatinga previously updated basis U_(i(i−2))′ with a previously determined(l−1)-th precoding vector V_(i(l−1))′l , e.g., as follows:

U _(i(l−1)) ′=[U _(i(l−2)) ′V _(i(l−1))′]  (5)

In some demonstrative embodiments, a beamforming precoding matrix,denoted V_(i)′, for the i-th user device may be formed by combining theN_(SS) precoding vectors corresponding to the i-th user, e.g., asfollows:

V _(i) ′=[V _(i1) ′V _(i2) ′ . . . V _(iN) _(SS) ′]  (6)

In some demonstrative embodiments, wireless communication unit 110 mayrepeat the calculations described above with reference to Equations 1,2, 3, 4, 5 and/or 6, e.g., to determine K beamforming precoding matricescorresponding to the K user devices, respectively.

In some demonstrative embodiments, wireless communication unit 110 maydetermine a beamforming matrix, denoted B′, to be used for performing MUMIMO transmission 113, to the K user devices, based on the K beamformingprecoding matrices. For example, wireless communication unit 110 maydetermine the beamforming matrix B′ by concatenating the K beamformingprecoding matrices, e.g., as follows:

B′=[V ₁ ′V ₂ ′ . . . V _(K)′]  (7)

In some demonstrative embodiments, wireless communication unit 110 maytransmit multi-user MIMO transmission 113 using the beamforming matrixB′.

In some demonstrative embodiments, the beamforming matrix determinedaccording to the operations described above with reference to Equations1, 2, 3, 4, 5, 6 and/or 7 may be substantially near optimal, forexample, at relatively high levels of Signal-to-Noise-Ratio (SNR), forexample, when inter-user interferences may be dominant, e.g., comparedto receiver thermal noise.

Reference is made to FIG. 2, which schematically illustrates a method ofmulti-user MIMO communication, in accordance with some demonstrativeembodiments. In some demonstrative embodiments, one or more of theoperations of the method of FIG. 2 may be performed by one or moreelements of a system, e.g., system 100 (FIG. 1), e.g., one or morewireless communication devices, e.g., wireless communication devices102, 104, 106 and/or 108 (FIG. 1), one or more wireless communicationunits, e.g., wireless communication units 110 and/or 124 (FIG. 1), and/or any other element. In some embodiments, one or more of the operationsof the method of FIG. 2 may be performed as part of a MBD algorithm,e.g., including one or more of the operations described above withreference to Equations 1, 2, 3, 4, 5, 6 and/or 7.

As indicated at block 202, the method may include receiving at awireless communication device a plurality of channel feedbacktransmissions from a plurality of user devices, respectively. A channelfeedback transmission from a user device of the user devices may includepartial information relating to a multi-user MIMO channel matrix betweenthe wireless communication unit and the user device. For example,wireless communication unit 110 (FIG. 1) of wireless communicationdevice 102 (FIG. 1) may receive a plurality of channel feedbacktransmissions from wireless communication devices 104, 106 and/or 108(FIG. 1), e.g., as described above.

As indicated at block 201, the method may include transmitting a channelfeedback transmission from at least one user device, e.g., from each ofthe user devices, to the wireless communication device.

In some demonstrative embodiments, the channel feedback transmission mayrepresent, for example, a plurality of eigenvectors corresponding to theMIMO channel matrix between the user and the wireless communicationdevice. For example, wireless communication unit 124 (FIG. 1) of thei-th user may transmit to wireless communication unit 110 (FIG. 1) achannel feedback transmission representing the matrix V_(i), e.g., asdescribed above with reference to FIG. 1.

As indicated at block 204, the method may include determining a MIMObeamforming scheme based on the plurality of channel feedbacktransmissions. In some demonstrative embodiments, determining the MIMObeamforming scheme may include determining the MIMO beamforming schemeaccording to a MBD algorithm. For example, wireless communication unit110 (FIG. 1) may determine the MIMO beamforming scheme based on thechannel feedback transmissions received from wireless communicationdevices 104, 106 and/or 108 (FIG. 1).

As indicated at block 208, determining the MIMO beamforming scheme mayinclude selecting the i-th user. For example, one or more of theoperations described below with reference to blocks 210, 212, 214, 216,218, 220 and/or 224 may be repeated with respect to one or more of theusers, e.g., for all of the users. Accordingly, at a first iteration,the method may include selecting, for example, a first user.

As indicated at block 210, determining the MIMO beamforming scheme mayinclude determining the interference matrix {tilde over (V)}_(i), e.g.,as described above with reference to Equation 1.

As indicated at block 212, determining the MIMO beamforming scheme mayinclude determining the SVD of the interference matrix {tilde over(V)}_(i), e.g., as described above with reference to Equation 2.

As indicated at block 214, the method may include determining a basis ofa space spanned by all the dominant eigenvectors of the users other thanthe i-th user. For example, determining the basis may includedetermining the basis Ũ_(i) ⁽¹⁾ including a set of eigenvectors of thematrix Ũ_(i) corresponding to non-zero singular values, e.g., asdescribed above.

As indicated at block 216, determining the MIMO beamforming scheme mayinclude determining the precoding vector V_(i1)′. For example,determining the precoding vector V_(i1)′ may include orthogonalizing thefirst eigenvector V_(i1) of the matrix V_(i) to the basis Ũ_(i) ⁽¹⁾,e.g., as described above with reference to FIG. 1.

As indicated at block 218, determining the MIMO beamforming scheme mayinclude determining an updated basis based on the basis Ũ_(i) ⁽¹⁾. Forexample, determining the updated basis may include determining the basisU_(i1)′ based on the basisŨ_(i) ⁽¹⁾ and the precoding vector V^(i1)′,e.g., as described above with reference to Equation 3.

As indicated at block 220, determining the MIMO beamforming scheme mayinclude determining a next precoding vector V_(i2)′. For example,determining the precoding vector V_(i2)′ may include orthogonalizing thesecond eigenvector V_(i2) of the matrix V_(i) to the updated basisU_(i1)′, e.g., as described above with reference to FIG. 1.

As indicated at block 222, determining the MIMO beamforming scheme mayinclude repeating the operations of blocks 218 and 220, e.g., untildetermining N_(SS) precoding vectors, e.g., as described above.

As indicated at blocks 224 and 225, determining the MIMO beamformingscheme may include increasing the value of i and repeating theoperations of blocks 208, 210, 212, 214, 216, 218, 220 and/or 222, forthe next user, for example, to determine K beamforming precodingmatrices corresponding to the K user devices, respectively, e.g., asdescribed above.

As indicated at block 226, determining the MIMO beamforming scheme mayinclude determining a beamforming matrix based on the K beamformingprecoding matrices. For example, determining the beamforming matrix mayinclude determining the matrix B′, e.g., as described above withreference to Equation 7.

As indicated at block 206, the method may include transmitting amulti-user MIMO transmission from the wireless communication device tothe plurality of users according to a MIMO beamforming scheme, which isbased on the plurality of channel feedback transmissions. For example,wireless communication unit 110 (FIG. 1) may transmit multi-user MIMOtransmission 113 (FIG. 1) using the beamforming matrix B′, e.g., asdescribed above.

Reference is made to FIG. 3, which schematically illustrates a graph 302depicting ergodic capacity as a function of SNR for a multi-user MIMOtransmission utilizing channel feedbacks including partial MIMO channelinformation, in accordance with some demonstrative embodiments.

Graph 302 depicts ergodic capacity results, in units of bits per secondper Hertz (Hz), with respect to an 8×2 antenna configuration with threeuser devices and N_(SS)=2 streams and a channel according to model D ofIEEE802.11TGac.

Graph 302 depicts the ergodic capacity achieved by a MBD algorithm,e.g., as described above with reference to FIG. 2. As shown in FIG. 3,the results according to the MBD algorithm may be similar to the resultsusing a conventional BD algorithm. However, it is noted that, incontrast to the conventional BD scheme, the MBD algorithm requirespartial MIMO channel matrix feedback information.

Referring back to FIG. 1, in some demonstrative embodiments, the channelfeedback transmission from one or more of the user devices may alsorepresent a channel quality indicator corresponding to a quality of achannel between the wireless communication unit and the one or more userdevices, respectively. For example, the first channel feedbacktransmission may represent a channel quality indicator corresponding toa quality of the channel between wireless communication unit 110 anduser device 104; the second channel feedback transmission may representa channel quality indicator corresponding to a quality of the channelbetween wireless communication unit 110 and user device 106; and/or thethird channel feedback transmission may represent a channel qualityindicator corresponding to a quality of the channel between wirelesscommunication unit 110 and user device 108.

In some demonstrative embodiments, the channel quality indicator from auser device may represent at least one of a SNR, aSignal-to-Noise-Interference Ratio (SINR), and a Modulation and CodingScheme (MCS) corresponding to the channel between wireless communicationunit 110 and the user device. In other embodiments, the channel feedbacktransmission may include any other suitable information relating toand/or representing the channel between wireless communication unit 110and the user device. Although some demonstrative embodiments aredescribed below with reference to the

SNR, other embodiments may be implemented with respect to any othersuitable channel quality indicator or parameter.

In some demonstrative embodiments, wireless communication unit 110 maydetermine the beamforming scheme for MU MIMO transmission 113 based onthe received channel quality indicators, e.g., as described below.

In some demonstrative embodiments, a vector basis may be determined,with respect to the i-th user, for a space spanned by scaledeigenvectors of all users other than the i-th user, for example, byeigenvalue decomposition of the following matrix:

{tilde over (V)} _(i) {tilde over (D)} _(i) {tilde over (V)} _(i) ^(H)+Ĩ _(M) _(T) =Ũ _(i) {tilde over (S)} _(i) Ũ _(i) ^(H)   (8)

wherein {tilde over (D)}_(i) denotes a diagonal matrix, e.g., asfollows:

{tilde over (D)} _(i)=diag(ρ₁₁ . . . ρ_(1N) _(SS) . . . ρ_((i−1)1) . . .ρ(i−1)N_(SS) ρ_((i+1)1) . . . ρ_((i+1)N) _(SS) . . . ρ_(K1) . . . ρ_(KN)_(SS) )  (9)

wherein ρ_(ij) denotes a SNR of a j-th stream of the i-th user, whereinj=1 . . . N_(SS),

wherein I_(M) _(T) denotes an identity matrix of a dimension M_(T),

wherein Ũ_(i) , denotes an unscaled basis matrix,

and wherein {tilde over (S)}_(i) denotes a scaling matrix.

In some demonstrative embodiments, an unscaled basis matrix, denotedU_(i)′, may be defined as follows:

U _(i) ′=Ũ _(i) {tilde over (S)} _(i) ^(−1/2)   (10)

In some demonstrative embodiments, the matrix V_(i) may be projected tothe space spanned by columns of the matrix U_(i)′. The matrix V_(i) maybe pre-multiplied by a square root of the diagonal matrixD_(i)=diag(ρ_(i1) . . . ρ_(iN) _(SS) ), for example, prior to projectingthe matrix V_(i), e.g., in order to reflect the contribution of the SNRof the N_(SS) streams. For example, the projection of the pre-multipliedmatrix V_(i) may yield a projected matrix, denoted V_(i)′, e.g., asfollows:

V _(i) ′=U _(i) ′U _(i)′^(H)(V _(i) D _(i) ^(1/2))=Ũ _(i) {tilde over(S)} _(i) ⁻¹ Ũ _(i) ^(H)(V _(i) D _(i) ^(1/2))   (11)

In some demonstrative embodiments, wireless communication unit 110 mayperform SVD of the projected interference matrix V_(i)′ of Equation 11,to yield:

V _(i) ′=Y _(i)Σ_(i) W _(i) ^(H)   (12)

wherein Y_(i) denotes a (M_(T)-by-M_(T)) unitary matrix over a field,denoted M′, which includes the matrix V_(i)′; wherein Σ_(i) denotes a(M_(T)-by-N_(SS)) diagonal matrix with nonnegative real numbers on thediagonal; wherein W_(i) denotes a (N_(SS)-by-N_(SS)) unitary matrix overM′; and wherein W_(i) ^(H) denotes a conjugate transpose of W_(i).

In some demonstrative embodiments, wireless communication unit 110 maydetermine K beamforming matrices corresponding to the K user devices,wherein the beamforming matrix for the i-th user, denoted Y_(i)^((1), may include the first N) _(SS) left dominant eigenvectors of thematrix V_(i)′.

In some demonstrative embodiments, wireless communication unit 110 maydetermine a beamforming matrix, denoted B″, to be used for performing MUMIMO transmission 113 to the K user devices based on the K beamformingmatrices. For example, wireless communication unit 110 may determine thebeamforming matrix B; ′ by concatenating the K beamforming matrices,e.g., as follows:

B″=[Y ₁ ⁽¹⁾ . . . Y _(K) ⁽¹⁾]  (13)

Reference is made to FIG. 4, which schematically illustrates a method ofmulti-user MIMO communication, in accordance with some demonstrativeembodiments. In some demonstrative embodiments, one or more of theoperations of the method of FIG. 4 may be performed by one or moreelements of a system, e.g., system 100 (FIG. 1), e.g., one or morewireless communication devices, e.g., wireless communication devices102, 104, 106 and/or 108 (FIG. 1), one or more wireless communicationunits, e.g., wireless communication units 110 and/or 124 (FIG. 1),and/or any other element. In some embodiments, one or more of theoperations of the method of FIG. 4 may be performed as part of a MRBDalgorithm, e.g., as described above with reference to Equations 8, 9,10, 11, 12 and/or 13.

As indicated at block 402, the method may include receiving at awireless communication device a plurality of channel feedbacktransmissions from a plurality of user devices, respectively. A channelfeedback transmission from a user device of the user devices may includepartial information relating to a multi-user MIMO channel matrix betweenthe wireless communication unit and the user device. The channelfeedback transmission from the user may also represent a channel qualityindicator corresponding to a quality of a channel between the wirelesscommunication device and the user. For example, wireless communicationunit 110 (FIG. 1) of wireless communication device 102 (FIG. 1) mayreceive a plurality of channel feedback transmissions from wirelesscommunication devices 104, 106 and/or 108 (FIG. 1), e.g., as describedabove.

As indicated at block 401, the method may include transmitting a channelfeedback transmission from at least one user device, e.g., from each ofthe user devices, to the wireless communication device.

In some demonstrative embodiments, the channel feedback transmission mayrepresent, for example, a plurality of eigenvectors corresponding to theMIMO channel matrix between the user and the wireless communicationdevice. For example, wireless communication unit 124 (FIG. 1) of thei-th user may transmit to wireless communication unit 110 (FIG. 1) achannel feedback transmission representing the matrix V_(i) and thechannel quality indicator, e.g., as described above with reference toFIG. 1.

As indicated at block 404, the method may include determining a MIMObeamforming scheme based on the plurality of channel feedbacktransmissions. In some demonstrative embodiments, determining the MIMObeamforming scheme may include determining the determining the MIMObeamforming scheme based on a MRBD algorithm. For example, wirelesscommunication unit 110 (FIG. 1) may determine the MIMO beamformingscheme based on the channel feedback transmissions received fromwireless communication devices 104, 106 and/or 108 (FIG. 1), e.g., asdescribed above.

As indicated at block 408, determining the MIMO beamforming scheme mayinclude selecting the i-th user. For example, one or more of theoperations described below with reference to blocks 410, 412, 414, 416,418 and/or 420 may be repeated with respect to one or more of the users,e.g., for all of the users. Accordingly, at a first iteration, themethod may include selecting, for example, a first user.

As indicated at block 410, determining the MIMO beamforming scheme mayinclude determining the interference matrix {tilde over (V)}_(i), e.g.,as described above with reference to Equation 1.

As indicated at block 412, determining the MIMO beamforming scheme mayinclude determining the SVD of a matrix, e.g., the matrix {tilde over(V)}_(i){tilde over (D)}_(i){tilde over (V)}_(i) ^(H)+I_(M) _(T) , whichis based on the interference matrix {tilde over (V)}_(i) and the channelquality information, e.g., the matrix {tilde over (D)}_(i)e.g., asdescribed above.

As indicated at block 414, the method may include determining theunsealed basis matrix U_(i)′ based on the SVD, e.g., as described abovewith reference to Equation 10.

As indicated at block 416, the method may include applying the channelquality information to the eigenvector matrix V_(i), for example, bypre-multiplying the matrix V_(i) by a square root of the diagonal matrixD_(i)=diag(ρ_(i1) . . . ρ_(iN) _(SS) ), e.g., as described above.

As indicated at block 418, the method may include projecting thepre-multiplied matrix V_(i) to the space spanned by columns of thematrix U_(i)′, e.g., as described above with reference to Equation 11.

As indicated at block 420, the method may include determining abeamforming matrix corresponding to the i-th user based on the projectedinterference matrix. For example, determining the beamforming matrixcorresponding to the i-th user may include performing SVD of theprojected interference matrix and selecting the first N_(SS) leftdominant eigenvectors of the matrix V_(i)′, e.g., as described above.

As indicated at blocks 422 and 423, determining the MIMO beamformingscheme may include increasing the value of i and repeating theoperations of blocks 408, 410, 412, 414, 416, 418, and/or 420 for thenext user, for example, to determine K beamforming matricescorresponding to the K user devices, respectively, e.g., as describedabove.

As indicated at block 424, determining the MIMO beamforming scheme mayinclude determining a beamforming matrix based on the K beamformingmatrices. For example, determining the beamforming matrik may includedetermining the matrix B″, e.g., as described above with reference toEquation 13.

As indicated at block 406, the method may include transmitting amulti-user MIMO transmission from the wireless communication device tothe plurality of users according to a MIMO beamforming scheme, which isbased on the plurality of channel feedback transmissions. For example,wireless communication unit 110 (FIG. 1) may transmit multi-user MIMOtransmission 113 (FIG. 1) using the beamforming matrix B″, e.g., asdescribed above.

Reference is made to FIG. 5, which schematically illustrates a graph 502depicting ergodic capacity as a function of SNR for a multi-user MIMOtransmission utilizing channel feedbacks including channel qualityindications and partial MIMO channel information, in accordance withsome demonstrative embodiments.

Graph 502 depicts ergodic capacity results, in units of bits per secondper Hz, with respect to an 8×2 antenna configuration with three userdevices and N_(SS)=2 streams and a channel according to model D ofIEEE802.11TGac. Graph 502 depicts the ergodic capacity achieved by aMRBD algorithm, e.g., as described above with reference to FIG. 4. Asshown in FIG. 5, the results according to the MRBD algorithm may besimilar to the results using a conventional RBD algorithm. However, itis noted that, in contrast to the conventional RBD algorithm, the MRBDalgorithm requires partial MIMO channel matrix feedback information.

Reference is made to FIG. 6, which schematically illustrates an articleof manufacture 600, in accordance with some demonstrative embodiments.Article 600 may include a machine-readable storage medium 602 to storelogic 604, which may be used, for example, to perform at least part ofthe functionality of wireless communication unit 110 (FIG. 1) and/orwireless communication unit 124 (FIG. 1), and/or to perform one or moreoperations of the methods of FIGS. 2 and/or 4.

In some embodiments, article 600 and/or machine-readable storage medium602 may include one or more types of computer-readable storage mediacapable of storing data, including volatile memory, non-volatile memory,removable or non-removable memory, erasable or non-erasable memory,writeable or re-writeable memory, and the like. For example,machine-readable storage medium 602 may include, random-access memory(RAM), dynamic RAM (DRAM), Double-Data-Rate DRAM (DDR-DRAM), synchronousDRAM (SDRAM), static RAM (SRAM), read-only memory (ROM), programmableROM (PROM), erasable programmable ROM (EPROM), electrically erasableprogrammable ROM (EEPROM), Compact Disk ROM (CD-ROM), Compact DiskRecordable (CD-R), Compact Disk Rewriteable (CD-RW), flash memory (e.g.,NOR or NAND flash memory), content addressable memory (CAM), polymermemory, phase-change memory, ferroelectric memory,silicon-oxide-nitride-oxide-silicon (SONOS) memory, a disk, a floppydisk, a hard drive, an optical disk, a magnetic disk, a card, a magneticcard, an optical card, a tape, a cassette, and the like. Thecomputer-readable storage media may include any suitable media involvedwith downloading or transferring a computer program from a remotecomputer to a requesting computer carried by data signals embodied in acarrier wave or other propagation medium through a communication link,e.g., a modem, radio or network connection.

In some embodiments, logic 604 may include instructions, data, and/orcode, which, if executed by a machine, may cause the machine to performa method, process and/or operations as described herein. The machine mayinclude, for example, any suitable processing platform, computingplatform, computing device, processing device, computing system,processing system, computer, processor, or the like, and may beimplemented using any suitable combination of hardware, software,firmware, and the like.

In some embodiments, logic 604 may include, or may be implemented as,software, a software module, an application, a program, a subroutine,instructions, an instruction set, computing code, words, values,symbols, and the like. The instructions may include any suitable type ofcode, such as source code, compiled code, interpreted code, executablecode, static code, dynamic code, and the like. The instructions may beimplemented according to a predefined computer language, manner orsyntax, for instructing a processor to perform a certain function. Theinstructions may be implemented using any suitable high-level,low-level, object-oriented, visual, compiled and/or interpretedprogramming language, such as C, C++, Java, BASIC, Matlab, Pascal,Visual BASIC, assembly language, machine code, and the like.

Functions, operations, components and/or features described herein withreference to one or more embodiments, may be combined with, or may beutilized in combination with, one or more other functions, operations,components and/or features described herein with reference to one ormore other embodiments, or vice versa.

While certain features of the invention have been illustrated anddescribed herein, many modifications, substitutions, changes, andequivalents may occur to those skilled in the art. It is, therefore, tobe understood that the appended claims are intended to cover all suchmodifications and changes as fall within the true spirit of theinvention.

What is claimed is:
 1. A wireless communication device including: awireless communication unit to transmit a multi-usermulti-input-multi-output (MIMO) transmission to a plurality of userdevices according to a MIMO beamforming scheme, wherein the wirelesscommunication unit is to receive a plurality of channel feedbacktransmissions from the plurality of user devices, respectively, whereina channel feedback transmission from a user device of the user devicesrepresents a plurality of eigenvectors corresponding to a MIMO channelmatrix between the wireless communication unit and the user device, andwherein the wireless communication unit is to determine the MIMObeamforming scheme based on the plurality of channel feedbacktransmissions.
 2. The wireless communication device of claim 1, whereinthe multi-user MIMO transmission includes two or more transmissionstreams directed to the user device, and wherein a number of theplurality of eigenvectors represented by the channel feedbacktransmission is equal to a number of the transmission streams.
 3. Thewireless communication device of claim 1, feedback transmissionrepresents a plurality of dominant eigenvectors corresponding to arespective plurality of dominant eigenvalues of the channel matrix. 4.The wireless communication device of claim 1, wherein the wirelesscommunication unit is to determine the MIMO beamforming scheme based onthe plurality of eigenvectors corresponding to the user device, andbased on a plurality of interference matrices corresponding to theplurality of user devices, respectively, wherein an interference matrixcorresponding to the user device includes a plurality of eigenvectorscorresponding to other user devices of the plurality of user devices. 5.The wireless communication device of claim 1, wherein the channelfeedback transmission represents a channel quality indicatorcorresponding to a quality of a channel between the wirelesscommunication unit and the user device, and wherein the wirelesscommunication unit is to determine the beamforming scheme based on thechannel quality indicator.
 6. The wireless communication device of claim5, wherein the channel quality indicator represents at least one of asignal-to-noise-ratio, a signal-to-noise-interference ratio and amodulation and coding scheme.
 7. The wireless communication device ofclaim 1, wherein the feedback transmission includes a codebook indexrepresenting a plurality of predefined vectors approximating theplurality of eigenvectors of the channel matrix.
 8. The wirelesscommunication device of claim 1, wherein the multi-user MIMOtransmission includes two or more transmission streams directed to eachone of the user devices.
 9. A wireless communication system including: awireless communication device including: a plurality of antennas; and awireless communication unit to transmit a multi-usermulti-input-multi-output (MIMO) transmission to a plurality of userdevices according to a MIMO beamforming scheme, wherein the wirelesscommunication unit is to receive a plurality of channel feedbacktransmissions from the plurality of user devices, respectively, whereina channel feedback transmission from a user device of the user devicesincludes partial information relating to a MIMO channel matrix betweenthe wireless communication unit and the user device, and wherein thewireless communication unit is to determine the MIMO beamforming schemebased on the plurality of channel feedback transmissions.
 10. Thewireless communication system of claim 9, wherein the channel feedbacktransmission represents a plurality of eigenvectors corresponding to thechannel matrix.
 11. The wireless communication system of claim 10,wherein the multi-user MIMO transmission includes a plurality oftransmission streams directed to the user device, and wherein a numberof the plurality of eigenvectors represented by the channel feedbacktransmission is equal to a number of the transmission streams.
 12. Thewireless communication system of claim 10, wherein the feedbacktransmission represents a plurality of dominant eigenvectorscorresponding to a respective plurality of dominant eigenvalues of thechannel matrix.
 13. The wireless communication system of claim 10,wherein the wireless communication unit is to determine the MIMObeamforming scheme based on the plurality of eigenvectors correspondingto the user device, and based on a plurality of interference matricescorresponding to the plurality of user devices, respectively, wherein aninterference matrix corresponding to the user device includes aplurality of eigenvectors corresponding to other user devices of theplurality of user devices.
 14. The wireless communication system ofclaim 10, wherein the feedback transmission includes a codebook indexrepresenting a plurality of predefined eigenvectors corresponding to theplurality of eigenvectors of the channel matrix.
 15. The wirelesscommunication system of claim 9, wherein the channel feedbacktransmission represents a channel quality indicator corresponding to aquality of a channel between the wireless communication unit and theuser device, and wherein the wireless communication unit is to determinethe beamforming scheme based on the channel quality indicator.
 16. Thewireless communication system of claim 9, wherein the multi-user MIMOtransmission includes two or more transmission streams directed to eachone of the user devices.
 17. The wireless communication system of claim9 including the user device.
 18. A method including: at a wirelesscommunication device, receiving a plurality of channel feedbacktransmissions from a plurality of user devices, respectively, wherein achannel feedback transmission from a user device of the user devicesincludes partial information relating to a multi-input-multi-output(MIMO) channel matrix between the wireless communication unit and theuser device; and transmitting a multi-user MIMO transmission to theplurality of user devices according to a MIMO beamforming scheme,wherein the MIMO beamforming scheme is based on the plurality of channelfeedback transmissions.
 19. The method of claim 18, wherein the channelfeedback transmission represents a plurality of eigenvectorscorresponding to the channel matrix.
 20. The method of claim 19, whereinthe multi-user MIMO transmission includes a plurality of transmissionstreams directed to the user device, and wherein a number of theplurality of eigenvectors represented by the channel feedbacktransmission is equal to a number of the transmission streams.
 21. Themethod of claim 19, wherein the feedback transmission represents aplurality of dominant eigenvectors corresponding to a respectiveplurality of dominant eigenvalues of the channel matrix.
 22. The methodof claim 19 including determining the MIMO beamforming scheme based onthe plurality of eigenvectors corresponding to the user device, andbased on a plurality of interference matrices corresponding to theplurality of user devices, respectively, wherein an interference matrixcorresponding to the user device includes a plurality of eigenvectorscorresponding to other user devices of the plurality of user devices.23. The method of claim 18, wherein the channel feedback transmissionrepresents a channel quality indicator corresponding to a quality of achannel between the wireless communication unit and the user device. 24.The method of claim 18, wherein the multi-user MIMO transmissionincludes two or more transmission streams directed to each one of theuser devices.
 25. A wireless communication device including: a wirelesscommunication unit to transmit a channel feedback transmission to awireless communication station, wherein the channel feedbacktransmission represents a plurality of eigenvectors corresponding to amulti-input-multi-output (MIMO) channel matrix between the wirelesscommunication unit and the wireless communication station, wherein thewireless communication, unit is to receive from the wirelesscommunication station a plurality of transmission streams of amulti-user transmission according to a MIMO beamforming scheme, andwherein the beamforming scheme is based on the channel feedbacktransmission.
 26. The wireless communication device of claim 25, whereinthe feedback transmission represents a plurality of dominanteigenvectors corresponding to a respective plurality of dominanteigenvalues of the channel matrix.
 27. The wireless communication deviceof claim 25, wherein a number of the plurality of eigenvectors is equalto a number of the plurality of transmission streams.
 28. The wirelesscommunication device of claim 25, wherein the channel feedbacktransmission represents a channel quality indicator corresponding to aquality of a channel between the wireless communication unit and theuser device.